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  • 11
    Electronic Resource
    Electronic Resource
    Exercise-induced hypoxemia in athletes: Role of inadequate hyperventilation (1992)
    Springer
    European journal of applied physiology 65 (1992), S. 37-42 
    Details
    ISSN: 1439-6327
    Keywords: Alveolar-arterialPO2 difference ; Pulmonary gas exchange ; VO2max ; Hypoxia ; Hyperoxia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary These experiments examined the exercise-induced changes in pulmonary gas exchange in elite endurance athletes and tested the hypothesis that an inadequate hyperventilatory response might explain the large intersubject variability in arterial partial pressure of oxygen (P a02) during heavy exercise in this population. Twelve highly trained endurance cyclists [maximum oxygen consumption (VO2max) range = 65-77 ml·kg−1·min−1] performed a normoxic graded exercise test on a cycle ergometer toVO2max at sea level. During incremental exercise atVO2max 5 of the 12 subjects had ideal alveolar to arterial P02 gradients (P A-aO2) of above 5 kPa (range 5-5.7) and a decline from restingP aO2 (ΔP aO2) 2.4 kPa or above (range 2.4-2.7). In contrast, 4 subjects had a maximal exercise (P A-aO2) of 4.0-4.3 kPa with ΔP aO2 of 0.4-1.3 kPa while the remaining 3 subjects hadP A-aO2 of 4.3-5 kPa with ΔP aO2 between 1.7 and 2.0 kPa. The correlation between PAO2 andP aO2 atVO2max was 0.17. Further, the correlation between the ratio of ventilation to oxygen consumption VSP aO2 and arterial partial pressure of carbon dioxide VSP aO2 atVO2max was 0.17 and 0.34, respectively. These experiments demonstrate that heavy exercise results in significantly compromised pulmonary gas exchange in approximately 40% of the elite endurance athletes studied. These data do not support the hypothesis that the principal mechanism to explain this gas exchange failure is an inadequate hyperventilatory response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01466272
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  • 12
    Electronic Resource
    Electronic Resource
    Mechanisms and dynamics of mechanical strengthening in ligament-equivalent fibroblast-populated collagen matrices (1993)
    Springer
    Annals of biomedical engineering 21 (1993), S. 289-305 
    Details
    ISSN: 1573-9686
    Keywords: Collagen ; Fibroblasts ; Ligament ; Stiffness ; Crosslink ; Collagen gel ; Breaking strength
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We have measured the dynamics of extracellular matrix consolidation and strengthening by human dermal fibroblasts in hydrated collagen gels. Constraining matrix consolidation between two porous polyethylene posts held rigidly apart set up the mechanical stress which led to the formation of uniaxially oriented fibroblast-populated collagen matrices with a histology resembling a ligament. We measured the mechanical stiffness and tensile strength of these ligament equivalents (LEs) as a function of age at biweekly intervals up to 12 weeks in culture using a mechanical spectrometer customized for performing experiments under physiologic conditions. The LE load-strain curve changed as a function of LE age, increasing in stiffness and exhibiting less plastic-like behavior. At 12 weeks, LEs had acquired up to 30 times the breaking strength of 1-week-old LEs. Matrix strengthening occurred primarily through the formation of BAPN-sensitive, lysyl oxidase catalyzed crosslinks. Sulfated glycosaminoglycan (GAG) content increased monotonically with LE age, reaching levels that are characteristic of ligaments. Cells in the LEs actively incorporated [3H]proline and [35S]sulfate into the extracellular matrix. Over the first three weeks, DNA content increased rapidly but thereafter remained constant. This data represent the first documentation of strengthening kinetics for cell-assembled biopolymer gels and the results suggest that this LE tissue may be a valuable model for studying the cellular processes responsible for tissue growth, repair, and remodeling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02368184
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  • 13
    Electronic Resource
    Electronic Resource
    Acid-induced esophagitis in cats is prevented by sucralfate but not synthetic prostaglandin E (1988)
    Springer
    Digestive diseases and sciences 33 (1988), S. 217-224 
    Details
    ISSN: 1573-2568
    Keywords: esophagitis ; sucralfate ; prostaglandin ; cytoprotection ; acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cytoprotective effects of liquid sucralfate and a synthetic analog of prostaglandin E1 (PGE1) on acid-induced esophagitis in cats were studied. Esophagitis was induced in adult cats using a constant infusion of 0.1 N HCl at 1 ml/min for 20 min. Animals were infused for either one or three days. Mucosal lesions were evaluated by blinded investigators using both fiberoptic endoscopy and light microscopy. Histologic changes included basal cell hyperplasia, intraepithelial leukocytosis, and subepithelial leukocytosis. Liquid sucralfate given prior to acid infusion consistently prevented acid-induced lesions in both one- and three-day infusions, demonstrated by both endoscopy and quantitative histologic scoring. Indomethacin (200 μg/kg) given prior to sucralfate and acid did not affect sucralfate cytoprotection. Synthetic PGE1, given in doses of 5 μg/kg and 100 μg/kg, afforded no esophageal cytoprotection. These studies indicate that sucralfate is cytoprotective against acid-induced esophageal injury in cats, an effect that does not appear to be mediated by prostaglandin. In addition, synthetic PGE1 does not confer protection in this animal model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01535736
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  • 14
    Electronic Resource
    Electronic Resource
    Experimental and theoretical investigation of extrudate swell of polymer melts from small (length)/(cross-section) ratio slit and capillary dies (1980)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 182-189 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An experimental and theoretical study is presented of extrudate swell from short capillary and slit dies. The polymer melts studied were polystyrene and polypropylene. The swell from slit dies is greater than the swell from capillaries. Decreasing die entry angle for capillary dies decreases swell. The argument is made that elongational How existing in the die entry region and for short dies determines extrudate swell. Dimensional analysis arguments are used to relate extrudate swell to a Weissenberg number based on elongational flow at the die entrance and the detailed die geometry. Correlations are developed. The theoretical study is based on unconstrained elastic recovery following elongational How through the die entrance region.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760200303
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  • 15
    Electronic Resource
    Electronic Resource
    Extrudate swell from slit and capillary dies: An experimental and theoretical study (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 609-616 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A comparative experimental study of extrudate swell from long slit and capillary dies is reported for rheologically characterized polystyrene and polypropylene melts. Generally extrudate swell from a slit is greater than that from a capillary die. At low die wall shear rates it goes to a value of about 1.2 as opposed to about 1.1 found for capillary dies. The onset and character of extrudate distortion have been studied. The experimental results are compared with theories of swell based on unconstrained recovery from Poiseuille flow in these geometries. A detailed analysis of such theories of extrudate swell based on the original work of Tanner has been carried out. The analysis is placed in a more general form which should be valid for a range of die cross-sections.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190904
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  • 16
    Electronic Resource
    Electronic Resource
    Extrudate swell and extrusion pressure loss of polymer melts flowing through rectangular and trapezoidal dies (1981)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 1101-1107 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A theoretical and experimental study of pressure losses and extrudate swell of flow through dies with complex crosssections is presented. The range of utility of models based on one-dimensional shearing on pressure loss-extrusion rate behavior is indicated. A procedure to predict extrudate profiles emerging from complex dies is developed. This is based on consideration of the idea of unconstrained elastic recovery from long dies. The theoretical predictions are contrasted with experiments on polystyrene and polypropylene.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760211609
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